In the mid-1990s, toxicologist Raymond Biagini was looking for a faster way to evaluate pest-control workers for exposure to pesticides. The existing process was slow and labor-intensive: Urine samples were hydrolyzed overnight in acid, extracted, cleaned, and then analyzed by gas chromatography or high-performance liquid chromatography. "And then at the end of all that, you have one number that took you a day and a half to get, minimum," says Biagini, of the Biomonitoring and Health Assessment Branch of the Centers for Disease Control and Prevention, and the National Institute of Occupational Safety and Health in Cincinnati, Ohio. Compounding this problem, most pesticide workers are exposed to four or five pesticides over the course of a week.